1. Field of the Invention
This specification relates to a plug interlock device for a vacuum circuit breaker.
2. Background of the Invention
Generally, a circuit breaker may be classified into a fixed type and a withdrawable type. The fixed type circuit breaker has only a body, and is fixed to inside of a panel of a switchboard. On the contrary, the withdrawable type circuit breaker has an outer case such as a cradle for facilitation of maintenance and repair, and is configured to insert or withdraw only a breaker body thereinto or therefrom.
The withdrawable type circuit breaker (hereinafter, will be referred to as ‘circuit breaker’) is accommodated in a switchboard together with other electric devices so as to drive a power plant, a substation, an electric motor, etc.
The circuit breaker may be configured such that the breaker body thereof is electrically connected to or separated from the cradle fixed to a switchboard. According to an accommodation position of the breaker body in the cradle, a position of the circuit breaker may be categorized into a ‘TEST’ position and a ‘RUN’ position. More concretely, the ‘TEST’ position indicates a position where only an operation test for the circuit breaker can be performed as a bus bar terminal and a load terminal of the breaker body are separated from a bus bar terminal and a load terminal of the cradle. On the contrary, the ‘RUN’ position indicates a position where a voltage and a current can be supplied as the bus bar terminal and the load terminal of the breaker body are connected to the bus bar terminal and the load terminal of the cradle.
In order to implement ON/OFF operations of the circuit breaker by transmitting an electric signal to the circuit breaker on a ‘RUN’ position or a ‘TEST’ position of the breaker body, required is an apparatus for applying power to the breaker body. To this end, a control power plug is installed at the switchboard, and a control power connector for connecting or disconnecting the control power plug is installed at the breaker body. If the breaker body is inserted into or withdrawn from the cradle in a state that the control power plug is not connected to the control power connector, or if the control power plug is disconnected from the control power connector on a ‘RUN’ position, the circuit breaker is not operated even if emergent situations occur. This may cause an accident. Accordingly, the circuit breaker has to be configured so that the control power plug may not be disconnected from the control power connector on a ‘RUN’ position or when the breaker body is inserted into or withdrawn from the cradle.
However, the conventional circuit breaker is not provided with an additional plug interlock device for a vacuum circuit breaker capable of preventing the control power plug from being disconnected from the control power connector on a ‘RUN’ position or when the breaker body is moved to a ‘RUN’ position from a ‘TEST’ position. As a result, a user may disconnect the control power plug form the control power connector by mistake on a ‘RUN’ position or when the breaker body is moved. This may cause an accident.